Python Lists for absolute beginners

“Python Lists for absolute beginners” will help you understand lists and how to begin working with Python list elements. In Python, lists let you hold data sets in one location, whether working with just a few or millions of items. Lists are Python’s most compelling components readily available to new programmers. They connect many vital concepts in Python programming.

What Is a Python List?

A Python list is a collection of items in a particular order. Your list includes letters of the alphabet, digits from 0–9, or nouns. A list can contain anything you like, and the items in your list don’t have to be connected in any distinct way. Because a list can usually hold more than a single element, it’s not a bad idea to make the name of your list in plural forms, like letters, digits, names, etc. In Python, square brackets “[]” indicates a list, and individual items are separated by commas. Next is a simple example of a list that holds some types of motorcycles: 

motorcycles= ['sport', 'off-road', 'scooters', 'mopeds'] print(motorcycles) 

When Python is asked to print a list, it returns the contents of the list, including the square brackets: 

['sport', 'off-road', 'scooters', 'mopeds'] 

Since you would want users to avoid seeing this kind of output, we’ll learn how to access the individual items in a list.

How to Access Elements in Python Lists

Lists are collections of ordered items, so you can access any element by telling using the location, or index, of the item chosen on the list. To access an element in a list, write the list’s name followed by the item’s index enclosed in square brackets. For example, let’s pull out the first motorcycle from the list of “motorcycles“:

motorcycles= ['sport', 'off-road', 'scooters', 'mopeds'] print(motorcycles[0]) 

Since Python uses zero “0” indexing, index “0” will return the first item on the list. When we request a single item from a list, Python will return only that element without square brackets or quotation marks:

sport

Your users should see a neatly formatted output like this. You can also use the string methods on any element in a list. For example, you can format the ‘sport’ more neatly by using the title() method: 

motorcycles= ['sport', 'off-road', 'scooters', 'mopeds'] 
print(motorcycles[0].title()) 

The output of this example will be the same as the initial example, except ‘Sport’ is capitalized.

Python Lists Index Positions Starts at 0, Not 1 

As I mentioned, Python considers the first item in a list to be at position 0, not position 1. This is true for most programming languages out there, and the reason is how the list operations are executed at a lower level. Suppose you are not getting the expected results. In that case, you might have made a simple off-by-one error (Off-by-one or OBO is when you predict something to have a value of N, but it ends up being N-1 or N+1). The second item in a list will have an index of 1. With this counting system, you can quickly get any element from a list by subtracting one from its position. For example, to get the fourth item in the list, you use index 3. The following gets for the motorcycle at index 1 and index 3:

motorcycles= ['sport', 'off-road', 'scooters', 'mopeds'] print(motorcycles[1]) 
print(motorcycles[3]) 

This code prints the second and fourth items on the list:

off-road
scooters

Python has a unique syntax for getting the last element on any. By using the index -1, Python will always return the last item on that list:

motorcycles= ['sport', 'off-road', 'scooters', 'mopeds'] print(motorcycles[-1]) 

This code will print ‘mopeds’. This syntax is very helpful since you’ll frequently like to access the last items in a list without paying attention to the length of the list. This way extends to other negative index values as well. Index -2 will return the second item from the end of the list, and index -3 will return the third item from the back, and so forth. 

How to Use the Values of Python Lists

Individual values from a list can be used just like any other variable. For instance, we can create a message based on values from a list using concatenation. Let’s get the first motorcycle from our motorcycles list and form a statement from the value. 

 msg = "I like " + motorcycles[1].title() + " Motorcycles." 
print(msg)

A massage was formed using the motorcycle[1] and stored in the variable msg. 

I like Off-road Motorcycles.

Time To Practice 

To have the concepts discussed in this tutorial at the tip of your finger will need some first-hand experience.

1. Try creating a list called “names” and add the names of people you know.
2. Try printing the items on your list one by one, and you can also use concatenation to make sentences out of them.
3. You can also play around with the item locations. You can also count forward and backward using the positive and negative indexes.

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